go smtp示例

刘光城 發表於 2022-3-13 21:04:00

书接上文<span class="cke_widget_wrapper cke_widget_inline cke_widget_csdnlink cke_widget_wrapper_link-info cke_widget_selected" data-cke-display-name="a" data-cke-filter="off" data-cke-widget-id="0" data-cke-widget-wrapper="1">邮件实现详解，这里我们及我们简单复习一下smtp的指令如下：
<div class="cnblogs_code">
<pre>telnet smtp.163.com 25

ehlo dz45693

auth login

输入用户名base64

输入密码base64
mail from:<dz45693@163.com>

rcpt to:<dz45693@sina.com>

data

from:<dz45693@163.com>
to:<dz45693@sina.com>
subject:hello world

This is the first email sent by hand using the SMTP protocol
.
quit　　</pre>
</div>
<img src="https://img2022.cnblogs.com/blog/209993/202203/209993-20220313182841054-2068185709.png">
好，那我们下现在用go实现代码让如下：这里只是一个demo，主要熟悉smtp命令
<div class="cnblogs_code">
<pre>package main

import (
"bufio"
"encoding/base64"
"fmt"
"net"
"strconv"
"strings"
)

func main() {
testSmtp()
}

var gConn net.Conn
var gRead *bufio.Reader
var gWrite *bufio.Writer

//可以放到这样的类里
type TcpClient struct {
Connnet.Conn
Read*bufio.Reader
Write *bufio.Writer
} //

func Connect(host string, port int) (net.Conn, *bufio.Reader, *bufio.Writer) {
addr := host + ":" + strconv.Itoa(port)
conn, err := net.Dial("tcp", addr)
if err != nil {
 return nil, nil, nil
}

reader := bufio.NewReader(conn)
writer := bufio.NewWriter(conn)

return conn, reader, writer
} //

//收取一行,可再优化
func RecvLine() string {
line, err := gRead.ReadString('\n') //如何设定超时?
if err != nil {
 fmt.Print(err)
 return ""
}

line = strings.Split(line, "\r")[0] //还要再去掉 "\r"，其实不去掉也可以
return line
}

func SendLine(line string) {
gWrite.WriteString(line + "\r\n")
gWrite.Flush()
}

//解码一行命令,这里比较简单就是按空格进行分隔就行了
func DecodeCmd(line string, sp string) []string {
tmp := strings.Split(line, sp)
var cmds = []string{"", "", "", "", ""} //先定义多几个，以面后面使用时产生异常
for i := 0; i < len(tmp); i++ {
 if i >= len(cmds) {
 break
 }
 cmds = tmp
}
return cmds
}

//读取多行结果
func RecvMCmd() string {
i := 0
rs := ""
mLine := ""
for i = 0; i < 50; i++ {
 rs = RecvLine() //只收取一行
 mLine = mLine + rs + "\r\n"
 if len(rs) < 4 {
 break
 } //长度要足够
 c4 := rs[4-1] //第4个字符
 if ' ' == c4 {
 break
 } //第4个字符是空格就表示读取完了//也可以判断 "250[空格]"
 }
return mLine
}

//简单的测试一下 smtp
func testSmtp() {
//连接
gConn, gRead, gWrite = Connect("smtp.163.com", 25)
defer gConn.Close()
//收取一行
line := RecvLine()
fmt.Println("recv:" + line)

//解码一下,这样后面的 EHLO 才能有正确的第二个参数
cmds := DecodeCmd(line, " ")
domain := cmds[1] //要从对方的应答中取出域名//空格分开的各个命令参数中的第二个

//发送一个命令
SendLine("EHLO" + " " + domain) //domain 要求其实来自 HELO 命令//HELO <SP> <domain> <CRLF>

//收取多行
line = RecvMCmd()
fmt.Println("recv:" + line)

//--------------------------------------------------
//用 base64 登录
SendLine("AUTH LOGIN")

//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

s := "dz45693" //要换成你的用户名,注意 163 邮箱的话不要带后面的 @域名部分
s = base64.StdEncoding.EncodeToString([]byte(s))
SendLine(s)

//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

s = "xxxxx" //要换成您的密码
s = base64.StdEncoding.EncodeToString([]byte(s))
SendLine(s)

//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

//--------------------------------------------------
//邮件内容
from := "dz45693@163.com"
to := "dz45693@sina.com"

SendLine("MAIL FROM: <" + from + ">") //注意"<" 符号和前面的空格。空格在协议中有和没有都可能，最好还是有
//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

SendLine("RCPT TO: <" + to + ">")
//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

SendLine("DATA")
//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

//发送邮件头
SendLine("from:<dz45693@163.com>")
SendLine("to:<dz45693@sina.com>")
SendLine("subject:hello world")
SendLine("") //发送空行后面就是邮件体
SendLine("This is the first email sent by hand using the SMTP protocol")

SendLine(".") //邮件结束符

//收取一行
line = RecvLine()
fmt.Println("recv:" + line)

SendLine("quit") //链接推出
line = RecvLine()
fmt.Println("recv:" + line)
} //</pre>
</div>
运行结果图下：
<img src="https://img2022.cnblogs.com/blog/209993/202203/209993-20220313183143346-1687104986.png">
 在go的sdk中提供了SendMail方法【发送邮件后这个方法会关闭链接】，实现如下：
<img src="https://img2022.cnblogs.com/blog/209993/202203/209993-20220313183749101-1222709924.png">
实现如下：
<div class="cnblogs_code">
<pre>func SendMailBySmtp(){
auth := smtp.PlainAuth("", "dz45693@163.com", "xxx", "smtp.163.com")
to := []string{"dz45693@sina.com"}
image,_:=ioutil.ReadFile("d:\\Downloads\\1.png")
imageBase64:=base64.StdEncoding.EncodeToString(image)
msg := []byte("from:dz45693@163.com\r\n"+
 "to: dz45693@sina.com\r\n" +
 "Subject: hello,subject!\r\n"+
 "Content-Type:multipart/mixed;boundary=a\r\n"+
 "Mime-Version:1.0\r\n"+
 "\r\n" +
 "--a\r\n"+
 "Content-type:text/plain;charset=utf-8\r\n"+
 "Content-Transfer-Encoding:quoted-printable\r\n"+
 "\r\n"+
 "此处为正文内容!\r\n"+
 "--a\r\n"+
 "Content-type:image/jpg;name=1.jpg\r\n"+
 "Content-Transfer-Encoding:base64\r\n"+
 "\r\n"+
 imageBase64+"\r\n"+
 "--a--\r\n")
err := smtp.SendMail("smtp.163.com:25", auth, "dz45693@163.com", to, msg)
if err != nil {
 fmt.Println(err)
}
}</pre>
</div>
运行效果
<img src="https://img2022.cnblogs.com/blog/209993/202203/209993-20220313184550091-406229720.png">
 
 示例如下：
<div class="cnblogs_code">
<pre>func SendMailByGomailOne(){
m := gomail.NewMessage()
m.SetAddressHeader("From", "dz45693@163.com", "dz45693")
m.SetHeader("To", "dz45693@sina.com")
m.SetHeader("Subject", "hello SendMailByGomailOne!")
m.Embed("d:\\Downloads\\1.png")
m.SetBody("text/html", "此处为正文121333!")

d := gomail.NewDialer("smtp.163.com", 25, "dz45693@163.com", "xxxx#")

if err := d.DialAndSend(m); err != nil {
 panic(err)
}
}</pre>
</div>
运行结果：
<img src="https://img2022.cnblogs.com/blog/209993/202203/209993-20220313185335209-1879091795.png">
来我们看看DialAndSend的实现如下： 
<div class="cnblogs_code">
<pre>package gomail

import (
"crypto/tls"
"fmt"
"io"
"net"
"net/smtp"
"strings"
"time"
)

// A Dialer is a dialer to an SMTP server.
type Dialer struct {
// Host represents the host of the SMTP server.
Host string
// Port represents the port of the SMTP server.
Port int
// Username is the username to use to authenticate to the SMTP server.
Username string
// Password is the password to use to authenticate to the SMTP server.
Password string
// Auth represents the authentication mechanism used to authenticate to the
// SMTP server.
 Auth smtp.Auth
// SSL defines whether an SSL connection is used. It should be false in
// most cases since the authentication mechanism should use the STARTTLS
// extension instead.
SSL bool
// TSLConfig represents the TLS configuration used for the TLS (when the
// STARTTLS extension is used) or SSL connection.
TLSConfig *tls.Config
// LocalName is the hostname sent to the SMTP server with the HELO command.
// By default, "localhost" is sent.
LocalName string
}

// NewDialer returns a new SMTP Dialer. The given parameters are used to connect
// to the SMTP server.
func NewDialer(host string, port int, username, password string) *Dialer {
return &Dialer{
 Host: host,
 Port: port,
 Username: username,
 Password: password,
 SSL: port == 465,
}
}

// NewPlainDialer returns a new SMTP Dialer. The given parameters are used to
// connect to the SMTP server.
//
// Deprecated: Use NewDialer instead.
func NewPlainDialer(host string, port int, username, password string) *Dialer {
return NewDialer(host, port, username, password)
}

// Dial dials and authenticates to an SMTP server. The returned SendCloser
// should be closed when done using it.
func (d *Dialer) Dial() (SendCloser, error) {
conn, err := netDialTimeout("tcp", addr(d.Host, d.Port), 10*time.Second)
if err != nil {
 return nil, err
}

if d.SSL {
 conn = tlsClient(conn, d.tlsConfig())
}

c, err := smtpNewClient(conn, d.Host)
if err != nil {
 return nil, err
}

if d.LocalName != "" {
 if err := c.Hello(d.LocalName); err != nil {
 return nil, err
 }
}

if !d.SSL {
 if ok, _ := c.Extension("STARTTLS"); ok {
 if err := c.StartTLS(d.tlsConfig()); err != nil {
 c.Close()
 return nil, err
 }
 }
}

if d.Auth == nil && d.Username != "" {
 if ok, auths := c.Extension("AUTH"); ok {
 if strings.Contains(auths, "CRAM-MD5") {
 d.Auth = smtp.CRAMMD5Auth(d.Username, d.Password)
 } else if strings.Contains(auths, "LOGIN") &&
 !strings.Contains(auths, "PLAIN") {
 d.Auth = &loginAuth{
 username: d.Username,
 password: d.Password,
 host: d.Host,
 }
 } else {
 d.Auth = smtp.PlainAuth("", d.Username, d.Password, d.Host)
 }
 }
}

if d.Auth != nil {
 if err = c.Auth(d.Auth); err != nil {
 c.Close()
 return nil, err
 }
}

return &smtpSender{c, d}, nil
}

func (d *Dialer) tlsConfig() *tls.Config {
if d.TLSConfig == nil {
 return &tls.Config{ServerName: d.Host}
}
return d.TLSConfig
}

func addr(host string, port int) string {
return fmt.Sprintf("%s:%d", host, port)
}

// DialAndSend opens a connection to the SMTP server, sends the given emails and
// closes the connection.
func (d *Dialer) DialAndSend(m ...*Message) error {
s, err := d.Dial()
if err != nil {
 return err
}
defer s.Close()

return Send(s, m...)
}

type smtpSender struct {
smtpClient
d *Dialer
}

func (c *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
if err := c.Mail(from); err != nil {
 if err == io.EOF {
 // This is probably due to a timeout, so reconnect and try again.
 sc, derr := c.d.Dial()
 if derr == nil {
 if s, ok := sc.(*smtpSender); ok {
 *c = *s
 return c.Send(from, to, msg)
 }
 }
 }
 return err
}

for _, addr := range to {
 if err := c.Rcpt(addr); err != nil {
 return err
 }
}

w, err := c.Data()
if err != nil {
 return err
}

if _, err = msg.WriteTo(w); err != nil {
 w.Close()
 return err
}

return w.Close()
}

func (c *smtpSender) Close() error {
return c.Quit()
}

// Stubbed out for tests.
var (
netDialTimeout = net.DialTimeout
tlsClient = tls.Client
smtpNewClient= func(conn net.Conn, host string) (smtpClient, error) {
 return smtp.NewClient(conn, host)
}
)

type smtpClient interface {
Hello(string) error
Extension(string) (bool, string)
StartTLS(*tls.Config) error
Auth(smtp.Auth) error
Mail(string) error
Rcpt(string) error
Data() (io.WriteCloser, error)
Quit() error
Close() error
}</pre>
</div>
 DialAndSend ,首先调用Dial方法创建连接，然后发送邮件，最后关闭链接，如果要频繁发邮件，那么是否保持长连接更好了？这里的Dial 调用了smtp.NewClient 创建smtp.Client对象c,然后调用c.Hello ,c.Auth，send 实际是调用c.Mail,c.Rcpt,c.Data，那么我们可以自己调用Dial方法然后循环调用send方法，最后在close。
代码如下：
<div class="cnblogs_code">
<pre>func SendMailByGomailTwo() {
d := gomail.NewDialer("smtp.163.com", 25, "dz45693@163.com", "xxx")
m := gomail.NewMessage()
m.SetAddressHeader("From", "dz45693@163.com", "dz45693")
m.SetHeader("To", "dz45693@sina.com")
m.SetHeader("Subject", "hello SendMailByGomailtwo!")
m.Embed("d:\\Downloads\\1.png")
m.SetBody("text/html", "此处为正文121333!SendMailByGomailtwo")

s, err := d.Dial()
if err != nil {
 panic(err)
}
defer s.Close()

err = gomail.Send(s, m)
if err != nil {
 panic(err)
}

m.Reset()
m.SetAddressHeader("From", "dz45693@163.com", "dz45693")
m.SetHeader("To", "dz45693@sina.com")
m.SetHeader("Subject", "hello SendMailByGomailthree!")
m.Embed("d:\\Downloads\\2.png")
m.SetBody("text/html", "此处为正文1SendMailByGomailthreeSendMailByGomailthree!")
err = gomail.Send(s, m)
if err != nil {
 panic(err)
}
}</pre>
</div>
运行结果：
<img src="https://img2022.cnblogs.com/blog/209993/202203/209993-20220313210346649-2056745953.png">
 

</div>
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来源：https://www.cnblogs.com/majiang/p/16001409.html

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go smtp示例